On Sunday, disabled athletes from all over the country will converge on New York to compete in the USA Triathlon Physically Challenged National Championships.

Competing in his fourth consecutive New York City triathlon will be Aaron Scheidies, 24, a three-time blind world champion.

Ever since the Michigan native’s high school cross-country coach encouraged him to compete in a mini triathlon, Mr. Scheidies knew he would devote much of his life to becoming an Ironman. “I got hooked and never looked back since then, even though I’ve been losing my vision over the years,” he said. In his six years of training since senior year of high school, he has taken the 2002, 2003, and 2005 World Triathlon Championship titles, enough achievement to prove that he is a man of hard work and persistence in the face of a life-changing disability.

Mr. Scheidies has been steadily losing his eyesight since he was 8. “When I was in third grade, my teachers noticed I wasn’t seeing the chalkboard and books, and for four or five years I went to every doctor in the state of Michigan,” he said.”I finally found out there is no cure; the cells in the center of my eye have died.” He can only see objects no more than 20 feet away, and even they appear as “blurry blobs.”

On Sunday, Mr. Scheidies will compete against 3,200 other disabled athletes and directly against other sight-impaired athletes in his age range in a race that starts at 100th Street and the Hudson River. The athletes must swim one mile down to 80th street, cycle up the West Side Highway 25 miles into the Bronx and back again, and then run 10 kilometers to the finish line in Central Park.

In line with his usual preparations, it seems Mr. Scheidies is well set for the obstacles ahead. “He comes to the city a day early, spends the day with someone from our staff, and physically memorizes every place he has to go,” a spokesman for the triathlon, John Korff, said.

In addition, Mr. Scheidies runs, swims, or cycles for one to two hours every day, though lately graduate school and a health complication have him going at a slower pace than his usual warp speed. During the Ironman triathlon last year, he damaged a nerve somewhere in his lower back that his doctors still can’t exactly locate.

On Sunday, his goal is to finish the race in two hours and 30 minutes, well slower than his personal best, two hours and four minutes. He said the race will mark his first time on a bicycle in a year.

Sight-impaired athletes like Mr. Scheidies can’t race without the help of guides, who swim, cycle, and run with the contestants. “Basically, the guide is my eyes,” he said.

Each contestant and guide uses a tether cord connected to their waists, and for the cycling portion of the race they ride a two-person bike. Mr. Scheidies said it’s been difficult to find a guide that keeps a pace that is faster than his, which is an ideal quality, as he relies on his guide not only for vision but for foresight.

The extra passion and effort the young athlete devotes to his races seem to permeate all facets of his life. He recently graduated from Michigan State University and is a member of Phi Beta Kappa. Currently, he’s in his first year at the University of Washington, where he is studying physical therapy.

It seems that none of his accomplishments has gone to his head. “Since I have an impairment, to succeed in life, I have to push myself harder to stay at the same pace as everyone else.”